
\begin{table}
\begin{center}
\begin{threeparttable}
\begin{tabular}{l c c c c}
\toprule
 & \multicolumn{2}{c}{TWFE estimator} & \multicolumn{2}{c}{CH estimator} \\
\cmidrule(lr){2-3} \cmidrule(lr){4-5}
 & (1) & (2) & (3) & (4) \\
\midrule
$\Delta\textrm{IPW}_{1900}$ (rounded) & $-0.019^{*}$ & $-0.013^{*}$ & $-0.034^{*}$        & $-0.022^{*}$        \\
                                      & $(0.006)$    & $(0.005)$    & $ [-0.052; -0.013]$ & $ [-0.060; -0.002]$ \\
\midrule
Initial Mf x year                     &              & x            &                     & x                   \\
N                                     & $1196$       & $1196$       & $730$               & $730$               \\
N switchers                           & $$           & $$           & $410$               & $410$               \\
\bottomrule
\end{tabular}
\begin{tablenotes}[flushleft]
\scriptsize{\item This table shows the results of regressions of Conservative vote share, 1900--1910 on the change in imports per worker. Models (1) and (2) use the conventional two-way fixed effects estimator used throughout the article. Models (3) and (4) use the estimator proposed by Chaisemartin and D'Haultfoeuille, which corrects for negative weights. This estimator directly compares units which changed treatment status from one period to the next against units which did not. In order to use this estimator, we round our $\Delta\textrm{IPW}$ measure to the nearest 0.5, and average the dependent variable over the two 1910 elections (for which the treatment is unchanged). All models control for constituency and year fixed effects, and (2) and (4) control for initial manufacturing interacted with year fixed effects. For models (1) and (2), standard errors clustered by county are shown in parentheses, for (3) and (4) we cluster bootstrap at the county level and report 95\% confidence intervals.  $^{*}p<0.05$ (or Null hypothesis value outside the confidence interval).}
\end{tablenotes}
\end{threeparttable}
\caption{Robustness of post-1900 voting results to
        Chaisemartin-D'Haultfoeuille estimator}
\label{table_ch_robust}
\end{center}
\end{table}
